Hi buddy,
This particular warning message generally appears in two cases (as far as i have come across):
1. When there are two objects, whose geometries are intersecting with each other, in which case changing the mesh priorities might help.
2. Secondly this error might appear in case of orphan objects(Note: Not every time orphan objects exhibit this phenomenon), which can be eliminated by adjusting the assembly parameters accordingly.

So, what i would suggest is, before you start meshing the geometry try to check your model using the Automatic case check tool from "Macros" tab. this will be helpful to some extent.
Let me know if my reply is helpful.
thanks
Pramodh J